Speaking to a youthful crowd at a midnight rally just hours before the first polls open today, the 30-year-old singer hailed Clinton as an advocate for the disadvantaged.
"No matter how absurd and mean he (Trump) became, she smiled bravely and she continued on," Gaga told a packed arena in the battleground state of North Carolina, hailing Clinton as "made of steel."
But the pop star urged respect for backers of Trump, who has described undocumented Mexican immigrants as "rapists," boasted of forcing himself on women and warned he may not accept an election loss.
"If we are true, true Americans, then we must go from viewing his followers as our adversaries to viewing them as our allies," she said.
More From This Section
Clad in a tight black pantsuit, Gaga left the podium to lead the crowd in dancing to her song "Come to Mama," which promotes civil discourse.
Gaga also performed her dance hit "Born This Way" and "Angel Down," a ballad that touches on race relations, before joining Jon Bon Jovi in a duet on the rocker's hit "Livin' on a Prayer."
A slew of prominent artists have performed to back Clinton during her campaign including Beyonce, Jay Z, Jennifer Lopez, Katy Perry, Pharrell Williams and Stevie Wonder.